Concentric pintle pump



Nov. 27, 1962 A. R. G RAD 3,065,711 CONCENTRIC PINTLE PUMP Filed April 21, 1961 4 Sheets-Sheefi; 1

ADOLF R. GRAD INVENTOR ATTORNEY Nov. 27, 1962 A. R. GRAD 3,065,711

CONCENTRIC PINTLE PUMP Filed April 21, 1961 4 Sheets-Sheet 2 ADOLF R. GRAD INVENTOR ATTORNEY v Nov. 27, 1962 Filed April 2;, 1961 4 Sheets-Sheet 4 yBZd FIG. 5

ADOLF R.GRAD

INVENTOR zwazzw.

ATTORNEY 3,@@5,7l l Patented Nov. 2?, 1962 3,065,711 QGNQENTRKQ PKNTLE PUM? q Adolf Richard Grad, Milwaukee, Wis assignor to The @ilgear Company, Milwaukee, Filed Apr. 21, 19M, Ser. No. 1814,6139 it Claims. (Ci. Elli-162) This invention relates to a hydrostatic machine such as a variable stroke axial type pump or motor in which motive fluid is conducted along the axis of trunnions which support a swingable cradle that carries the cylinder barrel for the machine.

In known devices of this type the swingable cradle provides inlet and outlet passages on opposite sides of the cradle for conduction through hollow pintles serving as trunnions for the support of the cradle. Since it is generally desirable to swing the cradle in a horizontal plane, the trunnion axis is therefore vertical, resulting in inlet and outlet ports in opposite trunnions appearing at the topand at the bottom of the machine. This arrange ment is found to be cumbersome and undesirable for rriany installations.

It is an object of the present invention to provide an improved pump or motor construction of the axial piston type having a swingable cradle for varying the displacement of the device wherein the upper trunnion serves as the conducting means for both the inlet and outlet passages for motive fluid. Another object of the invention is to provide a vertical pivot means for a swingable cradle for a pumping unit in which the pivot means provides both inlet and outlet ports on the top of the pumping unit.

Another object of the invention is to provide trunnions for a swinging cradle for a variable stroke axial type pump with the upper trunnion comprising an assembly easily insertable and removable from the housing for the pump and which includes, in addition to the inlet and outlet ports for the pump, bypass and surcharge valve means be tween the pump ports and a surcharge pressure relief valve.

Another object of the invention is to provide an axial type variable strokepump having a cradle swingable in a horizontal plane about a vertical axis provided by an upper and a lower trunnion in which the upper trunnion comprises an assembly that provides both the inlet and outlet ports for the pump and includes back pressure charging valves and bypass valves within the trunnion assembly, all internally connected so as not to require external piping, and provides for ready accessibility at the top of the pump.

These and other objects and advantages will be apparent from the following description of a preferred embodiment of the invention and from the accompanying drawings, in which:

FIG. 1 is a view in elevation and partly in section of a hydrostatic unit with a cradle pivotally supported on a vertical axis in the housing. FIG. 2 is a cross sectional view of the end portion of the cradle of FIG. 1 taken along the line 2--2.

FIG. 3 is a cross sectional view in elevation of another embodiment of an upper trunnion assembly in lieu of that provided for the pump shown in FIG. 1.

FIG. 4 is a cross sectional view taken along the line 4-4 of FIG. 3 to show the trunnion cap serving as a valve block for high pressure relief valves and surcharging valves.

FIG. 5 is a schematic view showing the arrangement of the valves incorporated in the trunnion cap and their connections with the pump ports and the gear pump.

Referring to FIG. 1, the variable stroke hydrostatic machine comprises a housing 6 having a main frame portion 7 that contains suitable ball bearings =8, 9 and a roller bearing ltl in which a drive shaft 2. is journalled. Secured to the housing 6 is a gear pump housing 13 through which the drive shaft 12 extends. A gear pump 17 (FIG. 5) is enclosed in the gear pump housing 13 and is suitably driven by the main shaft 32.

The gear pump 17 has an inlet supply provided by passages 14, 15 in the lower part of the main frame which may be mounted on and connected to a base serving as a reservoir 19. A gear pump outlet port 16 is provided in the top of the gear pump housing 113.

The drive shaft 12 terminates in a driving flange 18 which contacts the inner race of the adjacent bearing 10 to transmit axial thrust on the shaft to the inner races of angular contact ball bearings 8, 9.

A cradle 21 is pivotally supported about a vertical axis provided by an upper trunnion 22 and a lower trunnion 23 extending through the housing 6 and main frame 7.

A cylinder barrel 24 has a plurality of parallel cylinder bores 26 therein, only one of which is shown. The cylinder barrel is rotatably supported on a pair of axially spaced bearings 27, 28 on a central stud or stationary shaft 31 that extends through and is rigid with a yoke 29 of the cradle 21. Each cylinder bore 26 is provided with a piston 31 that is connected by an articulated rod 32 to the flange 1-8 of the drive shaft 2 for driving relation therewith in a known manner. A universal connection such as a Caradan shaft 33 is coupled to the drive shaft 12 and to the cylinder barrel 24 in a known manner, to provide synchronous rotation therewith.

A wear plate 34 is shown mounted on the end of the cylinder barrel 24 for rotation therewith and for cooperation with a distributor valve provided by a stationary ilat valve 36 having a well known arrangement of opposed arcuate high pressure and low pressure ports with which cylinder ports in the wear plate alternately register upon rotation of the cylinder barrel. Ports in the back face of the flat valve 36 are aligned with manifold passages 37, 33 in the end head portion or manifold 3% of the cradle. Holdup pistons ill, 41 are provided in the ports in the back side of the flat valve 36 to make sealing engagement with the face of the manifold 39' and to urge the flat valve axially against the wear plate 34, while being in constant communication respectively with the manifold passages 37, 38. The cylinder barrel 24 is rotatable and is radially and axially rigid; the fiat valve is non-rotatable but is axially movable in order to cooperate and make sealin engagement with the end of the cylinder barrel or its wear plate.

The manifold 39, FIGS. 1 and 2, is a cylindrical plug, forming the end of the cradle 21, and is inserted rigidly within a bore in the yoke 29 of the cradle. The yoke 29 is a casting comprising upper and lower legs or side members 29a, 29b, which are integrally joined at the end of the cradle. The yoke 29 supports the stationary central shaft 3t) which rotatably supports the cylinder barrel 24. The manifold 39 has four axial holes 37 which align with the holdup pistons as disposed in the flat valve which communicate with the upper port thereof, and the manifold has a group of four axial holes 38 in the,lower half thereof which align with the holdup pistons :31 which communicate with the lower port of the fiat valve. The dotted holes 42 indicated in the manifold represent bridge pistons disposed in the bridge portions of the flat valve which are those portions between the arcuate ports in the flat valve. The bridge pistons are supplied with pressure fluid in a known manner by the pressure in a cylinder port crossing the bridge portion. The upper group of four axial holes 37 is joined together by a pair of cross drilled holes 43, 44 which are arranged as an inverted V and joined together in a common radial hole 45 which aligns with a radial hole 46 extending into the upper leg 2% of u) the yoke, and is further axially extended by a passage 47 to the upper trunnion receiving bore 57 in the upper leg of the cradle yoke 29. The lower group of four holes 38 in the manifold is separately connected in pairs, respectively, by diverging bore holes 68, 49, respectively, which connect with parallel passages 51, 52 formed in the yoke and extending around the upper group of four holes 37 for common connection with a passage 53 in the upper side or leg 29a of the cradle yoke. This upper passage 53 is disposed radially of or superimposed above the other passage 47 in the leg and extends to the trunnion bore 57.

Lower trunnion 23 is provided by a bearing stud which is press fitted within bores 54, 55 in the bottom of the housing 6 and frame 7 and journalled through roller bearings 56 disposed within the lower leg 2% of the cradle yoke.

The upper trunnion 22 comprises an assembly that provides two parallel passages 64;, 63 that lead to inlet and outlet ports A and B respectively for the machine and also lead to passages 4-7, 53 in the upper leg of the cradle that connect with the corresponding ports of the distributor valve 36. The upper trunnion assembly preferably includes essentially a pair of tubular members or pintles 61, 62 concentrically arranged for a portion of their length and spaced apart to provide the fluid flow passages 63, 64. The radially outer pintle 61 is press fitted within bores 57, 58 in the housing 6 and frame 7 on the upper side of the machine and journalled in roller bearing 59 which is located in the upper leg 29:: closely adjacent frame 7, whereby the cradle 29 is swingable in a horizontal plane about the axis of bearings 56, 59.

The outer member or pintle 61 of the upper trunnion assembly has a relatively large hole or bore formed therein that extends axially of the pintle 61 to bottom on a shoulder 60 intermediate the ends of the pintle 61. A smaller bore within pintle 61 extends the bottom beyond shoulder 60 for receiving the inner tubular member or pintle 62 and securing it in a press fit and fluid tight relation at its bottom end. The inner tubular member or pintle 62 extends as a press fit through a bore in a cap member 65 and has a flanged upper end to abut the top shoulder of such bore. Cap member 65 has a larger coaxial bore for receiving the upper end of the outer member or pintle 61 in fluid tight relation. Cap member 65 has a flange abutting the housing and is secured thereto by bolts 67. Thus the cap 65 and the pintle 61 secure the pintle 62 in spaced concentric relation to pintle 61 to provide the concentric fluid flow passages 63, 64.

Cap member 65 has an end head secured thereto with a threaded hole defining the port A which aligns with and communicates with the inner tubular member and its flow passage 64. Cap member 65 has a radial hole 66 below the upper end of the inner pintle 62 such that hole 66 is in communication with the outer concentric flow passage 63. An end head 73 secured on the side of cap 65 is provided with a threaded hole that aligns with radial hole 66 and defines the port B for the machine.

A plurality of diametrically opposite radial holes 68 extend through the bottom portion of the trunnion 22 for establishing communication between the flow passage 64 in the inner tubular member 62 and the lower passage 47 in the upper side of the cradle yoke. An annular groove 69 is formed within the bore 57 of the cradle yoke in alignment and communication with these radial holes 68 and passage 47. Axially spaced above the lower group of radial holes in the trunnion is a group of radial holes 71 disposed at the bottom of the counter bore in pintle 61 which opens in to the outer coaxial flow passage 63, and these radial holes 71 are connected together by an annular passage 72 formed within the bore 57 of the cradle yoke for establishing communication with the upper passage 53 in the cradle yoke which extends to the manifold 39.

The upper trunnion assembly therefore provides parallel flow passages 63, 64 which connect the ports B, A, respectively, with flow passages 53, 47 in the upper leg of the cradle yoke and thereby avoid the use of the bottom trunnion 23 as a pintle. The construction and arrangement of the members of the upper trunnion assembly are hydrostatically balanced to the pressures within the flow passages because for each area subject to pressure of fluid within a passage there is an opposite equal area subject to the same pressure except for the inner pintle whose upper flange provides a greater area than its lower end; the resulting unbalance of forces on pintle 62 urges it downward so that its flange abuts the shoulder of the bore in cap 65. The hydraulic thrust forces exerted by the pumping forces tend to separate the drive shaft from the cylinder barrel and to separate the frame 7 from the cradle 21, and these thrust forces are taken up through the trunnions by the trunnion bearings 59, 56 which are located closely adjacent to the drive flange 18.

Means for swinging the cradle is provided by a torque arm 74 which is an extension of the upper leg 29a of the cradle yoke which forms a clevis joint through which a pin 75 is inserted and is available to couple a servo motor, not shown, such as a cylinder and an oppositely acting piston.

The upper trunnion assembly described may be inserted and removed as a unit and a modified upper trunnion assembly may be substituted therefor which, as shown in 165. 3, 4 and 5, incorporate high pressure relief valves, check valves, and low pressure relief valves, all interiorly connected Within the assembly without requiring external connection except to the output of the gear pump 17 and to drain, and which requires no other external connections except to a load device adapted to be connected to the main ports A and B.

The trunnion cap 77 is a valve block that has formed therein two main channels 83, 84, two cross channels 86, 37 that connect to the main channels and a common channel 86 disposed between the main channels and interconnecting the cross channels. Main channel 83 has a leading end portion 85 formed in the block and connects radially with the inner coaxial flow passage 64 and port A, as best seen in FIG. 3. Main channel 84 has a leading end portion 96 formed in the block and connects radially with the outer coaxial flow passage 63 and port B, as shown in FIGS. 3 and 4 and illustrated in FIG. 5.

The check valves 78, 79 are disposed in cross channel 36 on opposite sides of its junction with common channel 88, which serves as a surcharge chamber, and permit flow only from common channel 88 to the main channels 83, 84-. The high pressure relief valves 81, 82 are disposed in cross channel 87 on opposite sides of its junction with common channel 88 to relieve excess pressure from the main channels 83, 84, respectively, by operatively connecting the main channels to common channel 88. These high pressure relief valves 81, 82 are preferably balanced piston type of relief valves controlled respectively by pilot valves 81a, 82a which are mounted on the sides of the valve block closely adjacent their relief valves.

The pressure in the charging chamber provided by common channel 88 is limited to a predetermined rela tively low value by a surcharge relief valve 92 whose inlet is open to channel 88 and which has an outlet connected by a drain conduit 91 to the reservoir 19. Surcharge relief valve 92 also utilizes the block 77 for a valve body. Slot 98 in the cylindrical surface of piston 97 leads to a closed end chamber 99 wherein the lift area of the piston is subject to the pressure fluid for opening the valve.

Charging chamber provided by common channel 88 is also supplied with cool fluid from reservoir 19 by the gear pump 17 which normally provides pressure fluid to a control circuit through lines 93, 94. Gear pump relief valve 89 has an inlet conduit 95 connected to gear pump discharge line 93 and an output line 96 provided by a. drilled hole in block '77 that communicates with common channel 88 so that gear pump relief valve 89 discharges,

excess fluid into channel 83 to limit the pressure in the control circuit to a predetermined value.

Gear pump relief valve $9 may have a valve body separate from the valve block 77 but preferably it is integral therewith and located in superposed relation so that drain hole 96 extends downwardly therefrom for connection to channel 88 intermediate the cross channels 86, 87, whereas the other valves 78, 79, 81, 82 and 92 are located substantially in one horizontal plane. The inlet of surcharge relief valve 92 is connected to common channel 88 adjacent its connection with cross channel 87 which is the drain line from the high pressure relief valves, and the gear pump relief valve 39 has its discharge line 96 connected to channel 88 adjacent the cross channel 86 which supplies charging. fluid for fiow through one of the check valves for surcharging the pump inlet. This arrangement causes cool fluid from the gear pump to be used, when available, to replenish the pump circuit rather than the Warmer fluid discharged from the pump circuit by one of the high pressure relief valves, for this warmer fluid is thereby first to be returned to the reservoir 1% by the surcharge relief valve 92.

In operation of the pump when its displacement is in a direction such that pump port A is the pump discharge port and port B is the return or inlet port, then make up fluid necessary to maintain the inlet pressure at a positive value is supplied by gear pump 17 through gear pump relief valve, channel 88, and surcharge check valve 79 to the pump inlet. Excess fluid supplied to channel as that is below pump inlet pressure and above the setting of the low pressure relief valve 92 is returned thereby to reservoir 19.

Pump discharge pressure at port A is limited to the pressure setting of the pilot valve 31a which controls the high pressure relief valve ll which is operative to bypass fluid from port A to channel 88 for return to reservoir 19 through low pressure relief valve 92.

When pump displacement is such that pump port B is the pressure or discharge port, then gear pump fluid supplied to channel 88 is supplied to replenish pump inlet, now common to port A, through surcharge check valve 78. Pump discharge pressure at pressure port B is limited to the pressure setting of the pilot valve 32a which controls the high pressure relief valve 82 which is operative to bypass fluid from port B to channel 83 for return to reservoir 19 through low pressure relief valve 92.

Supply conduit 95 to gear pump relief valve 89 and drain conduit 91 from surcharge relief valve 92 are the only external lines connected to the trunnion cap assembly 7s that serves as a valve body 77 for the various valves that provide pressure relief and fluid replenishing for the pump circuit, except for the load connecting lines adapted to be connected to the pump ports A, B also provided by the trunnion cap assembly 76.

While only one embodiment of the invention and a modification thereof have been shown and described, others may be made from the teaching herein and within the scope of the appended claims.

I claim:

1. An axial piston rotating cylinder hydrostatic machine comprising a housing, a drive shaft rotatably supported in one end of said housing, a cylinder barrel rotatably supported in a cradle in the other end of said housing, first and second trunnions in opposite sides of said housing supporting said cradle for swinging movement about an axis transverse to said drive shaft to vary the stroke of the machine, a plurality of cylinders formed in said cylinder barrel with pistons therein connected by articulated means to said drive shaft, first and second passages in one side of said cradle, a distributor valve alternately connecting each cylinder with said first and second passages, first and second ports for said machine, said first trunnion providing inner and outer coaxial passages connected to said first and second ports respectively, a first radial passage in said first trunnion connecting said inner coaxial passage to said first passage in said cradle, and

a second radial pssage in sid first trunnion connecting said outer coaxial passage therein to said second passage in said cradle and said second trunnion serving only as a pivot support for said cradle, whereby said first and second pump ports are available for external connection at one side of said pump without any flow passages on the other side of said pump to said distributor valve.

2. The axial type hydrostatic machine of claim 1 wherein said first passage in said cradle is disposed radially under said second passage in said one side of the cradle and said cradle includes an end head portion serving as a manifold having an upper group of axial passages connected to one port of the distributor valve and a lower group of axial passages connected to the other port of the distributor valve, said upper group of axial passages being connected to a radial extension of said first passage in said cradle, and said lower group of axial passages being connected by diverging parallel flow paths around said first group and first passage to said second passage in said cradle.

3. An axial piston rotating cylinder hydrostatic machine comprising a housing, a drive shaft rotatably supported in one end of said housing, a cylinder barrel rotatably supported in a cradle in the other end of said housing, first and second trunnions in opposite sides of said housing supporting said cradle for swinging movement about an axis transverse to said drive shaft to vary the stroke of the machine, a plurality of cylinders formed in said cylinder barrel with pistons therein connected by articulated means to said drive shaft, first and second passages in one side of said cradle, a distributor valve alternately connecting each cylinder with said first and second passages, first and second ports for said machine, said first trunnion comprising concentric hollow pintles radially spaced apart intermediate their ends and being open to said first and second pump ports respectively, the outer said pintle being journalled in a bearing in said cradle, a first radial passage connecting the interior of the inner said pintle with said first passage in said cradle, a second radial passage connecting the interior of the outer said pintle with said second passage in said cradle, and said second trunnion journalled in a bearing in the other side of said cradle and serving only as a pivot support for said cradle.

4. An axial piston rotating cylinder hydrostatic machine comprising a housing, a drive shaft rotatably supported in one end of said housing, a cylinder barrel rotatably supported in a cradle in the other end of said housing, upper and lower trunnions in opposite sides of said housing supporting said cradle for swinging movement about an axis transverse to said drive shaft to vary the stroke of the machine, a plurality of cylinders formed in said cylinder barrel with pistons therein connected by articulated means to said drive shaft, first and second passages in one side of said cradle, a distributor valve alternately connecting each cylinder with said first and second passages, first and second ports for said machine, said trunnions journalled in hearings in opopsite sides of said cradle and rigidly secured to said housing, said upper trunnion having first and second ducts extending axially thereof and closed at the end portions toward said shaft and open at their opposite ends to provide the machine ports, annular chambers registering with said first and second passages in the cradle, and radial passages in said upper trunnion connecting said first and second ducts respectively to the first and second passages in the cradle through said annular chambers, whereby the machine ports are both available at upper side of the machine without flow passages in the lower side of the cradle from the distributor valve.

5. An axial piston type hydrostatic pump having a cylinder barrel rotatable in a cradle provided with trunnion hearings on a transverse axis, an upper trunnion and a lower trunnion secured in a housing for the pump and journalled in said hearings to support said cradle for swinging movement for varying the stroke of the pump,

said upper trunnion also iournalled in a bore in said upper side of said cradle having inlet and outlet passages therein for said pump, said upper trunnion providing a pair of passages extending axially thereof to inlet and outlet ports for the pump, and radial passages through said upper trunnion connecting said axial passages therein with said inlet and outlet passages, respectively, in the upper side of the cradle whereby said ports for said pump are located at the top side of the pump without flow passages in the bottom side of the cradle.

6. A variable stroke hydrostatic pump comprising a drive shaft, a cradle pivotally supported on a trunnion axis transverse to said shaft, a cylinder barrel rotatably supported in said cradle, pistons disposed axially in said cylinder barrel and connected by articulated rods to said shaft for driving said cylinder barrel and providing a stroke in accordance with the angular displacement of said cylinder barrel with said shaft, two trunnions on opposite sides of said pump providing said trunnion axis, inlet and outlet passages provided in one side of said cradle being connected by a distributing valve to said cylinder barrel, and one of said trunnions having passage means connecting said passages in said cradle to inlet and outlet ports, respectively, for the pump.

7. An axial piston rotating cylinder hydrostatic machine comprising a housing, a drive shaft rotatably supported on one end of said housing, a cylinder barrel rotatably supported in a cradle in the other end of said housing, first and second trunnions in opposite sides of said housing supporting said cradle for swinging movement about an axis transverse to said drive shaft to vary the stroke of the machine, a plurality of cylinders formed in said cylinder barrel with pistons therein connected by articulated means to said drive shaft, first and second passages in one side of said cradle, a distributor valve alternately connecting each cylinder with said first and second passages, first and second ports for said machine, said first trunnion providing a pair of coaxial passages with the inner one of said coaxial passages extending axially beyond the outer one of said coaxial passages, radial passages in said first trunnion connecting said coaxial passages to said inlet and outlet passages in said cradle, and means securing said first trunion in said casing and providing pump ports adapted for connection to an external circuit, whereby both said pump ports are available for connection at one side of the pump without any flow passages on the other side of the pump.

8. An axial piston rotating cylinder hydrostatic machin comprising a housing, a drive shaft rotatably supported in one end of said housing, a cylinder barrel rotatably supported in a cradle in the other end of said housing, first and second trunnions in opposite sides of said housing supporting said cradle for swinging movement about an axis transverse to said drive shaft to vary the stroke of the machine, a plurality of cylinders formed in said cylinder barrel with pistons therein connected by articulated means to said drive shaft, first and second passages in one side of said cradle, a distributor valve alternately connecting each cylinder With said first and second passages, a first and second ports for said machine, said first trunnion comprising a trunnion assembly including a pair of coaxial pintle members and a connecting trunnion cap secured to said housing, an outer one of said coaxial pintle members being extended through a bore in said housing and being journalled in a bearing in said one side of said cradle, an inner one of said coaxial members being spaced radially within the other intermediate the ends to define separate concentric flow passages, radial passages in said coaxial pintles connecting said first and second passages in said one side of said cradle with said coaxial flow passages, respectively, and said trunnion cap providing inlet and outlet ports connected, respectively, to said coaxial flow passages.

9. The hydrostatic pump of claim 8 in which said trunnion cap includes said inlet and outlet ports for the pump, inlet and outlet channels connected, respectively, to said concentric flow passages provided by said coaxial pintles and valve means operative to interconnect said inlet and outlet channels whereby said inlet and outlet pump ports and said valve means are provided only by said one trunnion assembly.

10. The hydrostatic axial type pump of claim 8 in which said trunnion cap includes said inlet and outlet ports for the pump and also serves as a valve body having opposed unidirectional valve means operatively connecting said ports to a source of predetermined pres sure.

References Cited in the file of this patent UNITED STATES PATENTS 1,523,079 Peabody Jan. 13, 1925 1,697,852 Coursen Jan. 8, 1929 2,530,242 Harrington Nov. 14, 1950 

